##### Symbols

A

area

a

attenuation

ac

attenuation coefficient

TA

temporal average

TP

temporal peak

SP

Spatial Peak

SA

Spacial Average

DF

Duty factor

AR

axial resolution

c

propagation speed

cos

cosine

ct

element propagation speed

d

diameter; distance to reflector; distance from transducer

DF

duty factor

df

focal beam diameter

F

f number

f

frequency

fD

Doppler-shift frequency

fl

focal length

fo

operating frequency

FR

frame rate

fR

received (echo) frequency

FRm

maximum frame rate

fT

transmitted (operating) frequency

I

intensity

Ii

incident intensity

Ir

reflected intensity

IRC

intensity reflection coefficient

It

transmitted intensity

ITC

intensity reflection coefficient

L

path length; tube length

LPF

lines per frame

LR

lateral resolution

n

number of cycles per pulse; number of foci;

ensemble

length

NL

Nyquist limit

P

power

p

pressure amplitude

PD

pulse duration

pen

penetration

PRF

pulse repetition frequency

PRP

pulse repetition period

Q

volumetric flow rate

R

flow resistance

r

radius

Re

Reynolds number

SPL

spatial pulse length

T

period

th

element thickness

v

flow speed, scatterer speed

va

average flow speed

vr

receiver speed

vs

source speed

wb

beam width

z

impedance

∆P

pressure difference; pressure drop

η

viscosity

θD

Doppler angle

θi

incidence angle

θr

reflection angle

θt

transmission angle

λ

wavelength

ρ

density

m

mass

F

force